6 Ways of Extracting Salt

The salt industry in the United State of America was one of the earliest mineral industries on earth that involved physically mining the salt from sea or from within the earth. Now, it has become a billion dollar industry and second only to the Chinese salt industry. In fact, the United States of America and China are responsible for producing 40% of the world’s quarter billion tons of salt produced every year! That’s a lot of salt!

The application of salt does not confine to food though. It is used in several other industrial processes and domestic uses such as manufacturing ice creams and melting frozen pavements. Even though salt’s presence may be ubiquitous, not many wonder about the methods used to extract and purify the quarter billion tons of salt that goes around every year!

Let’s go through some of those methods.

Evaporation:

This common method leaches salt out of rock salt layers lying at depths of around 400 meters by feeding in water and having the concentrated brine flowing through the pipelines and into the field collection tank. The extracted brine solution then goes through softening and crystallization in the evaporator plant. This type of common salt was referred to as evaporated or cooked salt.

Leaching/Drilling:

A typical leaching system consists of 3 pipes laid into boreholes. The innermost pipe carries the concentrated brine solution upward, the second pipe carries fresh water into the ground, and the third pipe pumps nitrogen as a protective measure to prevent quick leaching between the counter current brine and inflow of fresh water. The brine is then carried from the drilling field (that may stretch for several kilometers) to the collection tank where it can be seen as a clear liquid.

Brine purification/softening:

In this process, the raw brine from drilling field is eventually pumped into reactor tanks of the brine softening plant where impurities such as calcium and magnesium salts are removed from the brine. If the brine goes through the heating chamber, these secondary salts form a rock hard coating around the chamber walls, making the process less efficient each time. Therefore, precipitation involving the addition of quick lime, soda and carbon dioxide is used to precipitate these impurities out as gypsum and lime.

Crystallization:

Brine is passed through steam as hot as 140⁰C causing brine to evaporate as ‘flash steam’. Flash steam is then passed through the evaporator where salt crystallizes at the lower end as a wet paste.

Drying:

The wet paste then goes to the centrifuges where the centrifugal force is used to separate the water from salt, giving the resulting salt its signature snow white look. Then, hot airstream is used to drive any residual water out. This thorough process leaves only a few milliliters of water in every 100kg of salt.

Open cast mining:

Mining methods can be used to extract dry rock salt from salt containing saliniferous rocks. Most salt mines are present underground. However, in salt deserts, rock salt can be mined right off the surface too, through open cast mining. Rock salts form over thousands of years through the drying of primordial oceans and lagoons which left behind salt. Over the passage of time, rock formations over these salt layers embed them deep inside mountains or underground.

Rock salt offers versatile applications and can be used for many domestic and industrial purposes. If you’re looking for top quality USA grade rock salt, visit Rock Salt USA.